1. Field of the Invention
The present invention relates to a piezoelectric element including a piezoelectric layer formed of a piezoelectric material, and a liquid-jet head using the piezoelectric element as well as a liquid-jet apparatus.
2. Description of the Prior Art
A piezoelectric element is configured in a manner that a piezoelectric layer is interposed between two electrodes. The piezoelectric layer is made of, for example, a piezoelectric material showing an electrical mechanical conversion function. Alternatively, the piezoelectric layer is configured of, for example, crystallized piezoelectric ceramics.
There has been an inkjet recording head with the following configuration, as a liquid-head jet using such a piezoelectric element. In accordance with the configuration, a part of pressure generating chambers communicating with nozzle orifices from which ink droplets are ejected is constructed with a vibration plate. The vibration plate is deformed by piezoelectric elements, and thus ink in each of the pressure generating chambers is pressurized. Accordingly, ink droplets are ejected from each of the nozzle orifices. Two types of inkjet recording heads have been put into practical use. One of the two types uses a piezoelectric actuator of a longitudinal vibration mode in which the piezoelectric actuator expands and contracts in a longitudinal direction of piezoelectric elements. The other type uses a piezoelectric actuator of a flexure vibration mode.
As the inkjet recording head using the actuator of the flexure vibration mode, for example an inkjet recording head formed in the following manner has been known. An even piezoelectric layer is formed on the entire surface of a vibration plate by use of a film-forming technique. Then, this piezoelectric layer is cut into shapes corresponding to the pressure generating chambers by a lithography method. Thereby, the piezoelectric elements are formed respectively in the pressure generating chambers in a manner that the piezoelectric can be independent from one another.
Furthermore, as a piezoelectric layer (piezoelectric film) configuring such a piezoelectric element, there has been one made of lead zirconate titanate (PZT) (see Japanese Patent Laid-Open Official Gazette No. 2001-284671, for example). In this regard, various characteristics, such as displacement characteristics and durability, of the piezoelectric element including such a piezoelectric layer are largely dependent on crystallinity of the piezoelectric layer. Also in Japanese Patent Laid-Open Official Gazette No. 2001-284671, a relative permittivity, a coercive electric field and the like are regulated. However, it cannot be said that such a piezoelectric element disclosed in Japanese Patent Laid-Open Official Gazette No. 2001-284671 has sufficient crystallinity.
Note that, such problems are not limited to piezoelectric elements each installed in an inkjet recording head. It goes without saying that the problems are similarly present in other piezoelectric elements each installed in a liquid-jet head.